1. Field of the Invention
The present invention relates to a medical laser apparatus capable of selectively irradiating a plurality of visible laser beams each having a different wavelength onto an affected part of a body.
2. Description of the Related Art
As a medical laser apparatus such as a laser apparatus for use in photo coagulation treatment in ophthalmology, a type including a Raman fiber laser and a wavelength conversion element, for obtaining a plurality of visible laser beams each having a different wavelength that is suitable for the treatment at high intensity, has been proposed.
However, in the case of using the Raman fiber laser, a considerable number of fiber Bragg gratings having appropriate characteristics corresponding to the wavelength of an infrared beam, which is the source of a visible beam that is being sought, need to be combined, thereby complicating the structure and resulting in a high level of costs. Moreover, in order to obtain a plurality of infrared beams each having a different wavelength, which are the sources of a plurality of visible beams each having a different wavelength, a plurality of expensive Raman fiber lasers corresponding to the respective wavelengths of the infrared beams needs to be used. Further, the Raman fiber laser entails a problem insofar that the width of a spectrum of a Raman shifted infrared beam is likely to expand so that wavelength-conversion efficiency of its wavelength conversion element is reduced. Thus, if the intention is to obtain a visible beam of a level of more than 1 W (watt) that is necessary for the treatment, an excitation light source having a high level of output becomes necessary, thereby resulting in an expensive apparatus.